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Unit 2 > Connective Tissue Physiology (10/21a) [Biomedical] > Flashcards

Connective Tissue Physiology (10/21a) [Biomedical] Flashcards

1
Q

Tendon

A

parallel fibers, muscle to bone

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2
Q

Ligament

A

mostly parallel fibers, bone to bone

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3
Q

Tendon/Ligament Components

A

MAIN

  • cells
  • collagen fibers (types 1 and 3)

OTHERS

  • water
  • elastin
  • proteoglycans/GAGs
  • minor collagens
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4
Q

Proteoglycan/GAG function

A

negatively charged

attract water

help lubricate tissues

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5
Q

Viscoelastic Properties - Creep

A

application of constant load within elastic limit

transient change

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6
Q

Viscoelastic Properties - Stress Relaxation

A

application of constant deformation and over time the load becomes perceived as less stressful

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7
Q

Viscoelastic Properties - Cyclic Loading

A

when you load the tissue for repeated cycles, a few reps in is more reproducible than the first rep

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8
Q

Sprain vs Strain

A

Sprain — ligament or capsule

Strain — muscle or tendon

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9
Q

Sprain Grades

A

Grades 1 and 2 experience microtrauma, pain, some swelling

Grade 3 experiences macrotrauma, least stable, swelling, some pain

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10
Q

Microtrauma

A

small tears in CT and fibers that cause damage over time, caused by repetitive stress

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11
Q

Macrotrauma

A

caused by a traumatic event or forceful blow

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12
Q

Study of Injury Grades in Animals

A

We have tested tensile properties in animal models

Ultimate stress is greatly reduced in healing transected (macrotrauma) ligaments

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13
Q

Threshold for Injury

A

Consider Physical Stress Theory

For certain injuries, may have lower set points for thresholds

May have severely limited ultimate stress points

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14
Q

Three Phases of Tissue Healing

A

Acute Inflammation (0-5 days) — necessary to start healing process

Repair (3-28 days) — fibroblasts secrete collagen

Maturation/Remodeling (3 days-1 year) — improving the tensile strength of collagen

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15
Q

Tissue Healing - Acute Inflammation, Overview

A

(0-5 days)

Injury and Brief Vasoconstriction

Arterial Vasodilation
- edema formation

Clot Formation
- Prothrombin → Thrombin → Fibrin → Scar Tissue

Cellular Infiltration

Cytokine Production

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16
Q

Tissue Healing - Acute Inflammation, Treatment

A

Treat to control from spreading/worsening

POLICE

  • protect against further injury/inflammation
  • optimal loading to help recruit other cells
  • ice to vasoconstrict and reduce secondary inflammation and also control pain
  • compression and elevation to move the swelling away from the area
17
Q

Tissue Healing - Repair, Overview

A

(3-28 days)

Growth factor expression

  • produced mainly by activated macrophages & platelets (EX: IGF-1)
  • function – angiogenesis, proliferation of fibroblasts, collagen synthesis, collagenase secretion
  • proinflammatory cytokines — not good and can lead to negative cascade of events (EX: interleukin-1)

New vessel formation

Collagen synthesis exceeds lysis

Increased crosslinks (H+ bonding) - increasing tensile strength

Collagen Type III gradually replaced by Type I

Increased cells, GAGs, water

18
Q

Tissue Healing - Repair, Treatment

A

wrapping

open chain low load exercise

isometrics

stability and strength in distal and proximal

19
Q

Tissue Healing - Maturation, Overview

A

(3 days-1 year, can be up to 2 years)

Tendons and ligaments heal through scarring

Collagen synthesis = lysis

Conversion to type I collagen completed

More mature crosslinks (covalent)

Orderly alignment of collagen

Decreasing cellularity and vascularity

20
Q

Tissue Healing - Maturation, Treatment

A

Increasing difficulty of exercises, considering what other demands you can meet

Specific Adaptation to Imposed Demands (S.A.I.D) principle

EdUReP (Education, Unloading, Reloading, Prevention)
- EX: popular for tendinopathy

21
Q

3 Mechanisms of Loading/Unloading CT

A

Growth Factors

Stretch Activated Pathways

ECM Integrins

22
Q

CT Mechanism - Growth Factors

A

Growth factor receptors on the membrane and have a connection to the nucleus

Mechanically load tissue → growth factors released → bind to receptors

Signal transduction pathway activated → nucleus told to produce more collagen/fibroblasts

23
Q

CT Mechanism - Stretch Activated Pathways

A

Activate transduction signals that tell the nucleus to produce more collagen and fibroblasts

24
Q

CT Mechanism - ECM Integrins

A

Communicate to nucleus via integrins (proteins that are on cell membrane)

Tell nucleus to produce more collagen and fibroblasts

25
Q

Normal CT - Response to Loading

A

Consistent, prolonged exercise

Initiates a low‐level inflammatory response (acutely)

Upregulates collagenase synthesis (acutely)

Upregulates type I collagen synthesis (acutely & chronic)
- increased net type I collagen synthesis

26
Q

Normal CT - Response to Immobilization

A

Decreased collagen biosynthesis

  • decreased enzyme activities
  • decreased mRNA for type I & III collagen
  • appears to be stretch sensitive

Increased collagen degradation
- increased expression of matrix metalloproteinases (MMPs)

27
Q

Why don’t you want an over expression of matrix metalloproteinases (MMPs)?

A

you will get more collagen breakdown than you want

28
Q

Type 1 vs Type 3 Collagen

A

type 1 gives tensile strength (enzymatic crosslinks)

type 3 gives flexibility

29
Q

Healing CT - Response to Immobilization

A

BIOCHEMICAL

  • decreased collagen (decreased collagen synthesis, increased collagen lysis)
  • increased weak crosslinks
  • decreased GAG, HA, water content

MORPHOLOGIC
- adhesions, contractures, less orderly collagen fibers

BIOMECHANICAL

  • decreased tissue stiffness
  • decreased load to failure
30
Q

Examples of Healing CT’s response to immoblization

A

EX: decreased elastic modulus (stiffness)

  • decreased stiffness 6 weeks after repair
  • increased stiffness during cyclic loading

EX: increased creep
- deformation is much higher in scar tissue than normal tissue

EX: differences in collagen
- compared to normal ligament collagen, scar collagen is smaller, more uniform shape and size, but there are scar defects

31
Q

Healing CT - Response to Remobilization

A

BIOCHEMICAL

  • mechanical loading induces secretion of growth factors
  • increase collagen synthesis, ECM protein ‐ PGs

MORPHOLOGIC

  • in ambulatory rats, you see more cells at 3 weeks
  • in unloaded rats, you still see cells but not really in parallel structure

BIOMECHANICAL

  • people cannot withstand the same force they did before the injury
  • stiffness is highly decreased

Unit 2 (27 decks)

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